1. Field of the Invention
The present invention relates to mesoporous mixed oxide materials as a new class of SO2 resistant catalysts for hydrocarbon oxidation and a method for preparing the same. The mesoporous mixed oxide of this invention are ternary materials comprising lanthanum, a metal M selected from the group consisting of Cr, Mn, Fe, Co, Ni, Cu and Zn, and zirconium or cerium.
2. Description of Prior Art
The significant advantages of catalytic combustion of hydrocarbons include the more efficient use of energy source and minimum pollutant emissions as compared to convention flame combustion. Catalytic combustion at low temperature plays therefore an important role in energy supply for industrial and domestic applications. In the case of methane oxidation, the light-off point (defined as 10% conversion of the fuel stream) should ideally be achieved at a temperature of about 400° C. Therefore, in this context, catalytic materials should possess specific properties, such as high catalytic activity, low ignition temperature, long-term thermal stability, good resistance to poisoning agent and low cost.
Metal mixed oxide catalysts have been the subject of many investigations and have been recognized as active catalysts in a variety of catalytic processes such as hydrocarbon oxidation (Fokema, M. D. and Ying, J. Y., Catal Rev. Sci. Eng., 43, 2001, 1–29; A. J. Zarur and J. Y. Ying, Nature, 403, 2000, 65–67). Among them, perovskite type oxides containing transition metals (e.g., Co, Cr, Mn etc.) are considered of great interest for the combustion of hydrocarbon and NOx selective reduction etc. [Peña, M. A. and Fierro, J. L. G., Chem. Rev., 101, 101, 1981–2017; Tejuca, L. G. and Fierro, J. L. G. (Eds), Properties and Application of Perovskite-Type Oxides, Marcel Dekker Inc., New York, 1992; Kaliaguine, S., Van Neste, A., Szabo, V., Gallot, J. E., Bassir, M., and Muzychuk, R., Applied Catalysis A: General, 209, 2001, 345–358; Szabo, V., Bassir, M., Van Neste, A, and Kaliaguine, S, Applied Catalysis B: Environmental, 43, 2003, 81–92; Kaliaguine et al., U.S. Pat No. 6,017,504, 2000]. However, these materials usually possess low specific surface areas and are severely poisoned by a few ppm SO2. Their potential applications as catalysts are therefore limited. On the other hand, the discovery of surfactant-templated mesoporous molecular sieves with high surface area and uniform pore size [Kresge, C. T., Leonowicz, M. E., Roth, W. J. Vartuli, J. C., and Beck, J. S., Nature, 359, 1992, 710; Beck, J. S., Vartuli, J. C., Roth, W. J., Leonowicz, M. E., Kresge, C. T., Schmitt, K. D., Chu, C. T.-W., Olson, D. H, Sheppard, E. W., McCullen, S. B., Higging, J. B., and Schlenker, J. L., J. A. Chem. Soc., 114, 1992, 10834; Zhao, D., Feng, J., Huo, Q., Melosh, N., Frederickson, G. H., Chmelka, B. F., and Stucky, G. D., Science, 279, 1998, 548–552; Yang, P., Margolese, D. I., Chmelka, B. F., and Stucky, G. D., Nature, 396, 152] provided new opportunities for the synthesis of original catalysts [Kresge, C. T., Leonowicz, M. E., Roth, W. J. Vartuli, J. C., and Beck, J. S., Nature, 359, 1992, 710; Beck, J. S., Vartuli, J. C., Roth, W. J., Leonowick, M. E., Kresge, C. T., Schmitt, K. D., Chu, C. T.-W., Olson, D. H, Sheppard, E. W., McCullen, S. B., Higging, J. B., and Schlenker, J. L., J. A. Chem. Soc., 114, 1992, 10834; Zhao, D., Feng, J., Huo, Q., Melosh, N., Frederickson, G. H., Chmelka, B. F., and Stucky, G. D., Science, 279, 1998, 548–552; Yang, P., Margolese, D. I., Chmelka, B. F., and Stucky, G. D., Nature, 396,152; Trong On, D. and Kaliaguine, Angew. Chem. Int. Ed. Eng., 40, 2001, 3248-32–51; Trong On, D. and Kaliaguine, Angew. Chem. Int. Ed. Eng., 41, 2002, 1036]. The potential applications of these materials as catalysts were reported in a recent review [Trong On, D., Desplantier-Giscard, D., Danumah, C., and Kaliaguine, S., Applied Catalysis: General, 222, 2001, 299–357].